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Angus Grey, Mitchell Nye-Wood, Jeffrey Spraggins, Richard Caprioli, Kevin Schey, Paul Donaldson; Metabolite and lipid mapping in normal and functionally perturbed ocular lens by MALDI imaging mass spectrometry. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5738.
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© ARVO (1962-2015); The Authors (2016-present)
To assess changes in the distribution of ocular lens lipids and metabolites in physiologically perturbed lenses and in a model of age-related nuclear (ARN) cataract using MALDI (matrix-assisted laser desorption/ionisation) imaging mass spectrometry.
Bovine lenses were removed from the ocular globe and either frozen and stored at -80°C, or incubated in high K+ concentration artificial aqueous humor (to perturb lens function). Alternatively, lenses were incubated in normal artificial aqueous humor and subjected to 5 hour, 100% O2 treatment at 100 atm (to simulate ARN cataract). After freezing, lens cryosections (20μm) were collected on MALDI target plates via methanol landing. Matrix (9-aminoacridine) was applied by vacuum sublimation. MALDI imaging data sets were collected at 150μm spatial resolution using a MALDI-TOF or MALDI-FTICR mass spectrometer in negative ion mode. Detected small molecules were identified by accurate mass and tandem mass spectrometry approaches.
Hundreds of lipids and metabolites were detected in different regions of the ocular lens using MALDI imaging mass spectrometry. The distributions of several small molecules were altered upon physiological perturbation with high K+ artificial aqueous humor, and upon hyperbaric oxygen treatment. In normal lenses, while adenine nucleotides and glutathione were most abundant in the lens cortex, UDP-glucose, a precursor of glycogen, was abundant in the lens nucleus. The effect of lens functional perturbation on these and other small molecule distributions will be discussed.
MALDI imaging is a powerful imaging technique allowing simultaneous mapping of multiple small molecules, many for the first time, directly from tissue sections. Analysis of lipids and metabolites in normal and physiologically perturbed lenses enhances our understanding of the biochemical mechanisms underlying lens dysfunction.
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